Field of the Invention
The present invention relates to an electric apparatus including an electrically driven element configured to operate in response to receipt of a periodic signal, such as image projection apparatus and an image capturing apparatus.
Description of the Related Art
Image projection apparatuses often includes, in order to project a color image, three optical modulators (electrically driven elements) such as liquid crystal panels respectively modulating a red light, a blue light and a green light according to an input image signal. Moreover, some image capturing apparatuses such as a video camera are provided with three image sensors (electrically driven elements) respectively performing image capturing by photoelectrically converting optical images (object images) formed by a red light, a blue light and a green light, in order to record a color image. In such image projection and image capturing apparatuses, the three optical modulators and the three image sensors are often arranged around an optical element such as a prism efficiently introducing the red, blue and green lights to them; two of them are arranged such that their element surfaces (light entrance surfaces or image capturing surfaces) are mutually parallel and face toward the optical element.
The three optical modulators and the three image sensors are configured to operate mutually synchronously on a basis of a common synchronization signal. For this reason, the optical modulators and the image sensors whose element surfaces are mutually parallel each emit extraneous emission (EMI radiation) toward the other element surface, which results in a superposed extraneous emission whose intensity is high.
Japanese Patent Laid-Open No. 2011-152744 discloses a method of reducing the extraneous emission, in laser beam printers or laser copiers, by delaying a lighting timing of one of multiple laser diodes, which are originally to be lighted simultaneously, with respect to that of another of the laser diodes. Furthermore, Japanese Patent Laid-Open No. 2007-334416 discloses a method of reducing the extraneous emission, in laser beam printers or laser copiers, by intentionally dispersing phases of clock signals provided to multiple image processors and thereby mutually shifting phases of waveforms of electric currents consumed by operations of the image processors.
However, Japanese Patent Laid-Open Nos. 2011-152744 and 2007-334416 fail to disclose a measure to applicable to a case where, like the above-mentioned image projection and image capturing apparatuses, the extraneous emission is emitted from each of the electrically driven elements arranged mutually parallel toward the element surface of the other electrically driven element.